This invention relates generally to gas separation devices such as electrostatic precipitators and more particularly to an improved high-voltage discharge electrode assembly for extending the life of the discharge electrodes therein.
Electrostatic precipitators are used to remove foreign particles from a gas stream. They typically include a plurality of grounded collecting electrodes and high-voltage discharge electrodes suspended in spaced relationship to each other from supporting structure in precipitator shell.
The foreign particles in a gas stream moving between the electrodes of an electrostatic precipitator become negatively charged as a result of a high potential field set up between the collecting and discharge electrodes and are attracted to the grounded collecting electrode upon which they accumulate. A few of the particles may be attracted to the discharge electrodes and accumulate there. The accumulations on the electrodes are jarred loose by means of rappers or vibrators such as those shown in U.S. Pat. Nos. 2,922,085; 3,030,753; and 3,731,907.
The collecting electrodes are usually constructed of flat metal plates suitably connected together, whereas the discharge electrodes take the form of elongated wires, ribbons or rods suspended from the support structure. One means of suspending the discharge electrodes from the support structure has been to provide a shroud formed of a rigid piece of bar stock at the end of the discharge electrode as shown in FIG. 1 of the drawings. The discharge electrode is received within a hole in the end of the shroud and is retained therein by crimping or swaging the surrounding end of the shroud. While this known arrangement is relatively simple and economical to manufacture, it is disadvantageous in that it creates a stress point at the connection between the discharge electrode and the shroud which is subject to fatigue and mechanical failure from the rapping or vibrating of the electrodes. An area susceptible to corona discharge is also created in such an assembly.
There have been several attempts to avoid these problems associated with the type of discharge electode assembly illustrated in FIG. 1. For example, in U.S. Pat. No. 2,867,287 a discharge electrode construction is disclosed wherein each end of the discharge electrode is integrally formed into a spiral or coil spring section which, in turn, is received in a rigid tubular shroud member which may be attached to the precipitator support frame or from which a weight may be suspended. However, with such an arrangement the spring sections of the discharge electrode are normally under considerable tension because of the weight suspended from the lower end of the electrode. As a result of this tension and the relatively high temperatures in the electrostatic precipitators in which these discharge electrodes may be used, the coiled sections of the discharge electrode may lose their spring properties over time thereby increasing the likelihood of breakage of the electrodes.
More recently, a discharge electrode assembly for electrostatic precipitators was disclosed in U.S. Pat. No. 3,483,670 and employs a rigid shroud at each end of the discharge electrode. The shrouds are crimped upon the electrode wire to provide a mechanical connection which grips the electrode with graduated or tapering forces along the length of the crimp so as to reduce the severe localized stresses at the point of connection. That is, the crimped connections spread or distribute the stress through a much larger area so as to provide a longer service life for the electrode. However, with this known discharge electrode assembly breakage of the discharge electrode adjacent the crimped connection with the rigid shroud can still occur.
An object of the present invention is to provide an improved high-voltage discharge electrode assembly which extends the life of the electrode in an electrostatic precipitator as compared with the known arrangements wherein a rigid shroud is crimped to the electrode wire creating a stess point at the point of connection between the wire and the shroud which is subject to fatigue and mechanical failure.
A further object of the invention is to provide an improved high-voltage discharge electrode assembly which is simple and economical to manufacture and which retains its effectiveness in resisting breakage of the electrode from fatigue and mechanical failure even after considerable periods of operation in an electrostatic precipitator.
These and other objects are attained according to the invention by providing a high-voltage discharge electrode assembly for an electrostatic precipitator which comprises, in combination, an elongated discharge electrode, an anchoring element, one end of the elongated discharge electrode being secured at the anchoring element, and a flexible shroud member closely surrounding the elongated discharge electrode adjacent the anchoring element, whereby the life of the electrode in the electrostatic precipitator is extended.
In a disclosed, preferred embodiment the flexible shroud member comprises a spring which closely surrounds the elongated discharge electrode adjacent the anchoring element. The spring is a closely coiled, cylindrical helical spring.
According to an additional feature of the invention the flexible shroud member is secured to the elongated discharge electrode adjacent the anchoring element by a crimped portion of the flexible resilient shroud member which engages the electrode.
The end of the elongated discharge electrode secured at the anchoring element extends through a bore in the anchoring element and is formed with an enlarged, headed portion which secures the end of the electrode against axial displacement through the anchoring element. The anchoring element is in the form of a button with an outwardly tapered lower surface which may be received in an open keyhole slot in the support frame of an electrostatic precipitator for a suspending the discharge electrode from the support frame.
In the disclosed embodiment like assemblies are provided at each end of the discharge electrode. The anchoring element of the upper assembly is used to suspend the electrode from the support frame of an electrostatic precipitator. A weight is suspended from the lower anchoring element.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, one embodiment in accordance with the present invention .